At present, cassette players usually have respective operational functions: normal running (will hereinafter be described as FWD), reverse running (will hereinafter be described as REV), fast running (will hereinafter be described as FF), and rewind (hereinafter described as REW) of a tape.
In tape drive units which have been employed in such kinds of cassette players, there was proposed one which is provided with a cam gear having a cam face formed on its principal plane side, thereby for selectively switching the operation modes such as FWD, REV, FF, REW modes and so on.
In such tape drive unit, when the above-mentioned cam gear is rotated, a mode switching mechanism for switching to each operation mode is operated by means of the above-mentioned cam face. The rotational angle position of the cam gear and said each operation mode are made to correspond to each other. That is, by rotating the cam gear by a motor or the like and stopping it at a predetermined rotational angle for positioning, a predetermined operation mode is selected.
For instance, in the tape drive unit having a mode switching mechanism of a reverse-type recording/reproducing device, which is proposed in Japanese laid-open patent publication No. 62-163353 by the applicant of this case, the driving force of a single drive motor rotates and operates a pair of capstans for allowing a tape to travel to the FWD and REV sides, a reel shaft on which a tape reel is mounted for taking up the tape that was made to travel, and a cam gear for selectively switching a plurality of operation modes, respectively. That is, the driving force of the drive motor is transmitted to the capstans, reel shaft, etc. through a driving force transmission mechanism comprising a driving belt, gear and the like.
The cam gear has a gear portion having a plurality of tooth lacking portions formed on the outer periphery thereof, and has a predetermined cam face and a portion to be engaged which is protrusively provided on the major surface thereof. The cam gear is positioned through engagement of the portion to be engaged by a cam gear engaging member at a rotational angle position, at which the drive gear which transmits the driving force of the drive motor corresponds to the tooth lacking portions. The cam gear engaging member is constructed to be reciprocated by a plunger and an activating spring.
When the cam gear rotates, a mode switching mechanism for switching the operation mode is operated by the cam face. The mode switching mechanism is formed such that a predetermined operation mode can be selected by switching the transmission path of the driving force through an operation of moving the shaft of a gear for transmitting the driving force of the drive motor and by switching the travel direction of the tape through selectively pressing a pinch roller against the pair of capstans or the like.
That is, in the tape drive unit, to switch the operation mode, the plunger is actuated to release the engagement with the cam gear and engage the drive gear with the gear portion, thereby rotating the cam gear. Whereupon, the mode switching mechanism is operated and the tape traveling direction and the like are switched. The mode switching mechanism is operated according to the rotational angle position of the cam gear for switching to a predetermined mode corresponding to the rotational angle position. Accordingly, when the operation mode has been changed to a desired one, the desired operation mode is selected by releasing the actuation of the plunger and engaging and positioning the cam gear by the cam gear engaging member.
However, since the plunger has been required in the prior art as described above, there is a disadvantage that the cost will increase accordingly, and timing is important for the plunger trigger operation, in which a malfunction tends to occur, and the plunger itself is a part which easily malfunctions by the influence of dust and the like. In addition, a microcomputer is needed because of complicated control, which also leads to an increase in the cost, and malfunction also tends to occur due to bugs in the microcomputer. Moreover, there are various problems such as the need for care for resetting after battery replacement because of the electrical mode control, the difficulty of understanding the operation and the difficulty of service due to microcomputer control, and the like.
This invention was accomplished in view of such points, and the object of which is to provide a tape drive unit that requires no plunger and microcomputer thereby solving the above problems.